CHAP. III.] VERTEBRAE AND RIBS I MAN. 113 



the normal stands next behind it in ordinal sequence, we should 

 expect such backward Homceosis to be accompanied by reduction 

 in the total number of vertebrae ; so, conversely we should expect 

 forward Homceosis to be accompanied by an increase in total 

 number. This will be found to be sometimes the case {e.g. 

 No. 26). 



24. Male. C 7, D 13, L 5, S 5 [C not recorded]. 13 ribs on each 

 side. The right side differed considerably from the left. 



Right side. 1st rib resembled the usual supernumerary cervical, 

 being moveable and extending f- in. from its tubercle. Greater 

 part of ixth nerve crossed the neck of the rib ; just before doing so 

 it was joined by large branch of xth. The 2nd rib, borne by ninth 

 vertebra, in all respects resembled a normal 1st rib. The 3rd rib 

 articulated with sternum like a normal 2nd rib. In all, 8 ribs 

 articulated with sternum on right side, as usual. The 13th rib 

 (on 20th vertebra) was 4|- in. long. 



Left side. The 1st rib articulated with body and transverse 

 process of 8th vertebra, connecting with sternum in normal position, 

 but differing much from a normal 1st rib, being nearly straight 

 with very slight horizontal curve. 2nd rib normal in form and 

 direction; articulates with sternum J in. higher than right 3rd rib, 

 owing to the lower margin of manubrium being directed slightly 

 obliquely upwards and to the left. In all, 8 ribs articulated with 

 sternum, all below the first being at a level slightly higher than 

 that of the right ribs. The 13th rib (on 20th vertebra) was 4§ in. 

 long. Lane, W. Arbuthnot, J. Anat. Phys., 1885, p. 267 [full 

 description and discussion]. 



In this remarkable case, by the reduction of the 1st rib on the 

 right side, the 8th vertebra shews a forward Homceosis so far as 

 that side is concerned. The 20th vertebra, bearing a pair of 13th 

 ribs, also shews a forward Homceosis, but this seems to have been 

 a little greater on the left than on the right (cp. No. 20), the right 

 rib being a \ in. less in length. The fact that a large branch of 

 the Xth nerve on the right side joined the brachial plexus instead 

 of the usually minute fibre is specially noteworthy, as shewing a 

 forward Homceosis in the brachial plexus on the right side in 

 correlation to the similar Homoeosis appearing in the reduction of 

 the 1st rib on the same side. (Compare Nos. 14 and 25.) 

 25. Skeleton C 7, D 12, L 6 [S and C not recorded]. First pair 

 of ribs rudimentary, about 1^ in. long, exactly alike, as small 

 horns attached to 8th vertebra. Scalene muscles were inserted 

 into 2nd rib. The 25th vertebra was free, but the first lumbar 

 (20th vertebra) had no trace of a rib. Bellamy, E., J. Anat. Phys., 

 1885, p. 185. 



[In this case there is forward Homoeosis in the reduction of 

 the first ribs and in the formation of the 25th vertebra as a 

 lumbar, but there were no ribs on the 1st lumbar, which would 



b. 8 



